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Biology IB HL - 11.3 The Kidney Part 3
This deck covers essential concepts related to kidney function, focusing on ultrafiltration, selective reabsorption, and osmoregulation. It includes definitions, processes, and structural adaptations within the nephron.
What is ultrafiltration?
Blood is filtered out of the glomerulus at the Bowman’s capsule to form filtrate
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Key Terms
Term
Definition
What is ultrafiltration?
Blood is filtered out of the glomerulus at the Bowman’s capsule to form filtrate
What is selective reabsorption?
Usable materials are reabsorbed in convoluted tubules (both proximal and distal)
What is osmoregulation?
The loop of Henle establishes a salt gradient, which draws water out of the collecting duct
Where does ultrafiltration occur and give a definition?
It is the non-specific filtration of the blood under high pressure and occurs in the Bowman’s capsule of the nephron
What is the glomerulus encapsulated by?
This glomerulus is encapsulated by the Bowman’s capsule, which is comprised of an inner surface of cells called podocytes
What do podocytes have?
Podocytes have cellular extensions called pedicels that wrap around the blood vessels of the glomerulus
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| Term | Definition |
|---|---|
What is ultrafiltration? | Blood is filtered out of the glomerulus at the Bowman’s capsule to form filtrate |
What is selective reabsorption? | Usable materials are reabsorbed in convoluted tubules (both proximal and distal) |
What is osmoregulation? | The loop of Henle establishes a salt gradient, which draws water out of the collecting duct |
Where does ultrafiltration occur and give a definition? | It is the non-specific filtration of the blood under high pressure and occurs in the Bowman’s capsule of the nephron |
What is the glomerulus encapsulated by? | This glomerulus is encapsulated by the Bowman’s capsule, which is comprised of an inner surface of cells called podocytes |
What do podocytes have? | Podocytes have cellular extensions called pedicels that wrap around the blood vessels of the glomerulus |
What is between the podocytes and glomerulus? | Between the podocytes and the glomerulus is a glycoprotein matrix called the basement membrane that filters the blood |
What is the role of the basement membrane? | Blood is filtered by a mesh called the basement membrane, which lies between the glomerulus and Bowman’s capsule |
Why can blood freely leave the glomerulus? | Glomerular blood vessels are fenestrated (have pores) which means blood can freely exit the glomerulus |
How do podocytes allow for fluid to move freely? | The podocytes of the Bowman’s capsule have gaps between their pedicels, allowing for fluid to move freely into the nephron |
What is the sole filtration barrier in the nephron? | Consequently, the basement membrane functions as the sole filtration barrier within the nephron |
What does the basement membrane restrict? | The basement membrane is size-selective and restricts the passage of blood cells and large proteins |
Due to the basement membrane being size-selective, what is not in the filtrate? | Hence when the blood is filtered, the filtrate formed does not contain any blood cells, platelets or plasma proteins |
What is the role of ultrafiltration? | Ultrafiltration involves blood being forced at high pressure against the basement membrane, optimising filtration |
What creates the high hydrostatic pressure? | This high hydrostatic pressure is created in the glomerulus by having a wide afferent arteriole and a narrow efferent arteriole |
What is the role of the high hydrostatic pressure? | This means it is easy for blood to enter the glomerulus, but difficult for it to exit – increasing pressure within the glomerulus |
What other adaption does the glomerulus have? | Additionally, the glomerulus forms extensive narrow branches, which increases the surface area available for filtration |
What is the overall movement of blood in the glomerulus? | The net pressure gradient within the glomerulus forces blood to move into the capsule space (forming filtrate |
What is the second process in the nephron? | Selective reabsorption is the second of the three processes by which blood is filtered and urine is formed |
What is the role of selective reabsorption? | It involves the reuptake of useful substances from the filtrate and occurs in the convoluted tubules (proximal and distal) |
Where does the majority of selective reabsorption occur? | The majority of selective reabsorption occurs in the proximal convoluted tubule, which extends from the Bowman’s capsule |
How is the proximal convoluted tubule adapted for selective reabsorption? | The proximal convoluted tubule has a microvilli cell lining to increase the surface area for material absorption from the filtrate The tubule is a single cell thick and connected by tight junctions, which function to create a thin tubular surface with no gaps |
What organelle does the proximal convoluted tubule have a large number of? | There are also a large number of mitochondria within these tubule cells, as reabsorption involves active transport |
Where are substances actively transported in the proximal convoluted tubule? | Substances are actively transported across the apical membrane (membrane of tubule cells facing the tubular lumen) |
Where do substances passively diffuse in the proximal convoluted tubule? | Substances then passively diffuse across the basolateral membrane (membrane of tubule cells facing the blood) |